Effect of a nonuniform resistive wall on the stability of tokamak plasmas

Abstract

The effect of a nonuniform resistive wall on the stability of plasma magnetohydrodynamical (MHD) modes is examined. For the case of a tokamak plasma interacting with a wall possessing toroidally nonuniform electrical resistance, the kink mode dispersion relation is found to reduce to a surprisingly simple form, provided that the scale of variation of the resistance is sufficiently large. The influence of a wall with toroidal gaps on tokamak plasma stability is investigated in some detail. Under some circumstances, kink modes are found to ‘‘explode’’ through the gaps with ideal growth rates. A similar investigation is made for a modular wall constructed of alternate thick and thin sections.